1. Field of the Invention
The present invention is broadly concerned with an improved spirometry assembly for measuring one or more patient pulmonary parameters. More particularly, the invention pertains to a spirometry assembly including a spirometer having a base equipped with a reader (e.g., an elongated reading slot with an adjacent optical reader) and a disposable tubular sensor unit having at least one characterizing indicium thereon readable by the reader. Preferably, the sensor unit has a tab including at least one characterizing indicium thereon which characterizes a response parameter of the sensor unit upon flow of gas therethrough. In use, the tab is inserted within the base slot and the characterizing indicium is read to generate characterizing data for the specific sensor unit; a measuring device (e.g., a pressure transducer) is in operative communication with the interior of the sensor unit and is used to generate condition data during patient-induced inspiratory or expiratory gas flow through the sensor. The characterizing data and condition data are sent to a signal processor which generates a report about the pulmonary condition of the patient. The preferred sensor unit is equipped with a specialized pressure chamber which minimizes the possibility of pathogen contamination during use.
2. Description of the Prior Art
Spirometry is considered to be one of the most basic and important tests that measure pulmonary function, and is used in the prevention, diagnosis, observation and therapy of many pulmonary diseases such as chronic obstructive pulmonary disease (COPD). During spirometry, a patient induces an expiratory or inspiratory gas flow through a single-use, disposable sensor tube equipped with a restrictor. The pressure conditions within the sensor tube are measured via a sensitive pressure transducer, and this data is used to calculate in a microprocessor-based signal processor various pulmonary flow conditions such as forced vital capacity (FVC), forced expiratory volume in the first second of expiration (FEV.sub.1), FEV.sub.1 /FVC, forced expiratory volume in the third second of expiration (FEV.sub.3), mean flow rate between 25% and 75% of the FVC (FEF25-75%), peak expiratory flow (PEF), forced expiratory time (FET), forced inspiratory vital capacity (FIVC), peak inspiratory flow (PIF), ratio of forced inspiratory flow at 50% of FIVC to the forced expiratory flow at 50% of FEC (FEF50%/FIF50%) and maximal voluntary ventilation (MVV).
A persistent problem with existing spirometry systems stems from the fact that the single-use spirometry sensor tubes must be individually calibrated, or characterizing data for each such sensor tube must be provided as an input to the spirometer signal processor. For example, in one widely used spirometry system sold by Nellcor Puritan Bennett Corporation under the designation "Renaissance", the individual sensor tubes having screen-type restrictors are factory-calibrated to insure that pressure conditions therein during specified gas flow rate conditions are essentially constant. Such calibration operations are labor intensive and therefore relatively expensive.
It has also been known in the past to provide characterizing data with each individual sensor tube. In such systems, the user must enter the characterizing data into the spirometer so that such data can be used in the overall calculations leading to a pulmonary report. These systems suffer from the added complexity of requiring the user to enter the sensor tube characterizing data, and the possibility of data entry error which can lead to an entirely erroneous pulmonary report.
Some prior spirometry sensor tube equipment has been prone to contamination from aerosolized or other contaminants entrained within expiratory gas. This is a problem inasmuch as disease can be spread from patient-to-patient through the spirometry equipment.